Fall back to patterns if there are no concept link matches

[Twan Goosen]

The VLO importer never falls back to patterns if a profile has concept links for a given facet, even if there are no matches based on concept links. This should be an option. There is a potential for unexpected side effects, so this needs to be checked after implementation.

See #554 for a use case.

[herold@bbaw.de]

I don't understand which patterns are meant here. I'd expect the following behaviour:

Look for a metadata element that matches the facet description. If found: use the value (can be empty, though, i.e. "unspecified"). If not found: generate an "unknown" value.

[Twan Goosen]

Replying to herold@…:

I don't understand which patterns are meant here. I'd expect the following behaviour:

Look for a metadata element that matches the facet description. If found: use the value (can be empty, though, i.e. "unspecified"). If not found: generate an "unknown" value.

Patterns mean XPaths here. This ticket is about the places in the document that are even considered for looking for a value for a specific facet. The current behaviour is: if a profile has a matching data category, completely ignore any XPath that might match. So even if an instance of such a profile (a CMDI document) has no value in one of the fields matching the data category, the XPaths do not get checked either. To change its behaviour to fall back in such cases is what is proposed in this ticket.

[teckart@informatik.uni-leipzig.de]

Commited to trunk (r5985) - at least no evident problems with this new approach